Metallurgical process



Feb. 9 5,25

Wl. E. GREENAWALT METALLURGICAL PROCESS Filed Dec. 1. 1924 ufphlde Ore Or Conce RoasLmg Acxcgc Solv. 1cm Concentrated Furnace Oxide or Carbonair: 'B02256261 0f@ Cu Orc Leachmg 'Van H,

CLL

wash Water Overflow cen No1 ,semer Electrolgzed Solution SOZRecLuce'f N03 Cell No 5 HMT N05 Wash SOzRedlLcer N04' Cell New? umili Zn: NaOH NaOH Cao H255 OTT:

Clear H25 Preclplanr u SeparatorA @MMM E Solufloll To @ZZ iii/0m it may concern:

. tions, Serial No. (364,085, filed Sept. 21, 1923 l solution has to he diccarded and au equal atenteid. Fei). 9, 1926.

` leaching and electrolysis, and may be coness is applicable to. copper ores alone, or to 4.copper ores containing other metals, al-

:trolytic units, 'to the treatment of the dis-I WILLIAM n. 'GREENAWAL'L or DENVER, coronario.

METALLURGICAL PRocEss. l j

Application inea December 1, 1924. serial No. 753,134.

carded' foul solutions 4and to the lean wash Water t0 recover the copper from these solutions as the relatively pure electrolytic metal, and-to otherxrelated details.

l The process isrbest described by referring to theaccompanying,l drawing, which represents' a How sheet of the invention in diagrannnatic section.` f

The copperore, crushed to suitable lineness, is treated in the leaching tankwith a dilute acid solution to extract the copper, preferably in the form of sulphate. As all copper ores contain iron, the coppersulphate solution Will he contaminated with iron sulphate, and this iron sulphate may become Very injurious inthe electrolytic deposition of the copper. When the copper sulphate solution, containing ferrous sulphate, i s electrolyzed to deposit the copper, acid is `regenerated and at the same time some of thevferrous sulphate is oxidized to the ferrie sulphate, and thisA ferrie sulphate, coming in contact with -the deposited copper at the cat-hotles, re-dissolves the copper practically in proportion to the amount of ferric iron in the electrolyte. Theamount of ferrie iron in-the electrolyte should not exceed .0.25% for good Work; 0.5% has a decided detrimental etl'ect; and when the amount of ferrie iron reaches 1.0% theprocess` becomes Be it, known that I, VILLLUL E. GREENA- WALT, a. citizen of the United States, residing in the city and county of Denver and' State of Colorado, have invented certain new and useful Improvements in Metallurgical Processes, of which the following is a speciiication.

The invention is more specifically directed to theV extraction of copper from its ores by si'dered as an improvement on processes patented loy me as set forth in Patents No. 1,353,995, September 28, 1920, and No. 1,357,495, Nov. 2, 1920, and in my applica- (Patent No. 1,528,209, Mar. 3, 1925), and Serial. No. 689,013, tiled Jan. 31, 192i (Pac. ent No.-l,542,935, J une 23, 1925); The proclthough'it is not intended to limit its use to any particular application.

In the treatment of copper-ores by leaching and electrolysis, as set4 forth, for eX- ample, in Patent No. 1,353,995, it his heen found that excellent results are .obtained by passing the leach solution througi'h a series of electrolytic units, each comln-ising a reducer and a group of celle, or eltatrolyzers, in a sort of compound circuit, which consists in circulating` the solution or electrolyte in a practically clos-:ed circuit of each` electrolytic unit, and progressively advanc-v ing aportion of th-c solution or electrolyte, which may he termed Ihe advance iiow, through the series of elcctrolytic unile, and, then hack to the leaching'tank, where more. copper is taken into solution and the coniplete cycle repeated.

in carrying out this general process it is quite necessary to ctiectively and automatically regulate the lflow .of solution through the respectii'e electrolytic units. and as the solution or electrolyte becomes fouled with impurities a certain amount of the impure cal. While ferrie' iron in the electrolyte is highly detrimental, ferrous iron ie practically harmless, and may he decidedly heuelicial, .since it is capable of acting' energetically zs a depolarizing agent iii the deposition of the copper.

- Sulphur dioxide is in'eferrell 'as the general reducing' agent for the ferrie iron in the electrolyte, resulting from the deposition otl the copper from a copper solution containing vsalts of iron. Sulphur dioxide is 'more effective as a reducing` agent in neutral high in acid. In the deposition of copper from leach solutions, better efficiencies are obtained. with rich than 4with Weak solutions.l amount of water, preferably in the Aform of The significance of these points may he illuswash Water, has to he added to maintain the solution at a Acertain stand-ard 'of impurity of soluble salts.

The presentinvention pertainsfino're parl' ticularly to the automatic regulation of the flow of solution through the respective electhe leaching` tank (contains ,4.0% copper and it is desire'dto electrolytically precipitate the copper so that the depleted solutiony will contain 1.0%' copper before it is returned to the leaching tank in the cyclic operation of the' process: It is evident that Vthe copper 'or slightly acid solutions than in solutionsl so greatly impaired as to make it inipracti- 1 trated Yas follows: Suppose the solution from will have to be precipitated from a solution containing onl about 1.0% copper, and about 8.25% acid, assuming that Q Tilbs. of acid are regenerated per pound ofl copper precipitated. Under these conditions, the current efcienoy would be low, the reduction of the ferrie iron would be extremely diiiicult, and, the deposited copper would be quite impure. To meet the conditions indicated, it is preferred to proceed as follows: 'lhe'neutral'or-slightly acid leacli`solution from-the leaching tank, which for illustration purposes may be assumed to contain 4.0% copper and some soluble iron and other salts, flows intothe feed tank' No. 1, from which it flows in a' substantially constant and regulated'stream into S02 reducer No. 1, Where it is treated with sulphur dioxide from the roasting furnace to reduce the harmful ferrie iron 'to the harmlessferrous iron, with Ithe simultaneous regenerationA of an equivalent of acid. The reduced solution flows into the settler No. 1, where insoluble matter is settled out, and the clearoyertiowing solutiony flows into cell No. l, Wherethe copper is deposited and acid and ferrie iron regenerated. Cell No. 1 is intended to be a conventional indication of one or more cells, depending` on the size of thc cellsand the amount of copper to be deposited. The so- `lotion from cell No. 1, or electrolyzer, is then returned in a sort of closed circuit, toth'e reducer No. 1,'through the feed tank No. 1, where the ferrie iron formed by the electrolysis is again reduced. The solution issuing from-the cell should not exceed 0.25% for really good Work. The process is so refrulated that a portion of the solutionthe advance flow-oyertiows from feed tank No. 1 into feed tank No. 2, and into the SO2 re` ducer No. Q,and this solution will contain about 2.5%l copper and about 4.0% acid. From reducer No. if the solution flows into settler No. Q and cell No. 2, Where inore cop. per is deposited and more' acid aud-tiferric iron regenerated. `The solution, issuing from cell No. 2 is returned in a sort of' closed circuit to the reducer No. L) tl'iroughithc iced tank No. f2, while another portion-'the advance liowwis returned to the ore, and this advance flow will contain about 1.0% copper and about 8.25% acid, Most of the copper produced will be produced inA this'wayt and will represent the major output of the lant. i

In time7 lthe solution being circulated as.

'amount of water, preferably Wash Water, to keep the solution yat a 'certain approximatestandard for satisfactory operation. .y 'A relat1velysinall contlnuous stream of Lemire foul solution is diverted from the-main leaching and electrolytic circuit, or circuit No. 1, to a secondary circuit, or circuit No. 2, where most of the remaining copper is deposited from the foul solution electrolytically, and the remaining small portion of the copper is then precipitated chemical-ly,

`before the solution is wasted or treated to recover other metals.

The foul solution, under the assumed conditions for illustration purposes, will contain about '1.0% copper and about 8.25% acid, and iron and other salts. las already indicated, such a solution presents difficulties in electrolysis, duc largely to the ditli culty encountered in reducing the ferrie iron formed by the deposition of the copper. lt is preferred therefore to noix a certain amount of -Wash rater from the leaching tank with the foul solution to reduce both the acidity and the percentage of impurities. Some of the excess acid may be neutralized by adding` linie or caustic soda to the foul electrolyte. wWith the acid reduced, the ferrie iron is much more easilyreduced.

A small stream of foul solution, as dcvtei-mined by experience, is bled from circuit No. 2, into feed tank No. 3, of circuit No. S,

yand from the feed tank the foul solution,

preferably reduced in acidity, flows into reducer No. 3, where is is treated with a reducing agent, such assulphur dioxide.7 after which it flows into cell No. 3, where a certain amount of copper is deposited with the simultaneous regeneration of acid and ten ric salts. rlhe solution is then returned, through the feed tank No. 3 to the reducer No. 3, and the cycle continued, while a portion-the advance flow roes to *feed tank. No. Ll, to the SU, reducer ll'o. 4f, and the reduced solution flows into cell No. et, and the cycle is repeated until inost of the copper is deposited out'. of the foul solution. il..

neutralizing;- agent, such as linie or caustic. soda may bc added to the electrolyte as it ,flows into feed tanks No. il and No. l. lluder these conditions it has been found practical to deplete the foul solution'of copper down to about 0.10%, and with a fairly high aniperc etliciency, lt has also been found that the copper can be deposited in fairly good hard forni in cells-No. l, with theI eflluent solution as low as 0.25% copper, while the copper deposited in cell'No. et is likely to he granular or spongy, and quite impure, but the ampere 'e'ciency can be maintained fairly goed, especially with a lon.' current. density, or a current density lower than that used in circuit No. 1, and in circuit No. 5, to

be described later. lnhdepositing` the copper from the foul solutlons, 1t is preferred to use insoluble cathodes-such as lead sheets; that is to say cathode sheetsv` wliicli are insoluble when used as anodes. ltn cell No. o the copper `both the acidity and the deposited on the lead cathode sheetwill be.

be granular' or spongy and will not usually adhere to .the lead cathode sheets, but the.4

copper will drop from the lead sheet` cathodes from time to time, and can be accumulated in the bottom of the tanks.

lVhenthe cathodes in cell No.` 3 .have ac.- cumulated suiicient copper to make their removal desirable., the eathodes are transferred to. a` rich Copper electrolyte, as in cell No; 5, and used as anodes. In this Way the impure copper from the foul solutions is re-dissolved 'and is rte-deposited, at av comparatively small expense, as the pure electrolytie metal. There is an advantage inusing insoluble cathode sheets for this purpose. When the impure cathodes obtained from the foul solutions are Itransferred to the ricli copper solution and used as anodes, the copper will be transferred to pure' cathode sheets, and-When all the copper is re-dissolved, and re-deposited on the'pure catho-de sheets, the insoluble leadsheets, on which the impure copper lwas deposited, are again transferred to the foul solution in cell No. 3, and thev cycle repeated. lf the re-solu tion of the copper from the impure anodes, in cell No. `5 (transferred cathodes from cell No. 3) is uneven, it will not 'make a great deal of difference. lVhen the copper is removed from the lead sheets, the lead sheets will' act as insoluble -anodes, butvas the E. M. F. required to deposit copper from solutions with insoluble anodes is vabout 1.75 volts, under the assumed conditions, and about 0.3 volts for soluble' anodes, the impure copper will be removed from the lead sheets before the lead sheets,`

or exposed. portions of them, will act as insoluble anodes', so that no-unusual refinement will he necessary in this operation.

The copper deposited in cell No. 4 is ae- 4cumuluted in the bottom of the tank and removed from time to time. This granular or spongy copper is preferably applied to the rich electrolyte in unit'No. 5, where it is re-dissolvcd by using it as 'a reducing agent to reduce the ferrie iron formed in the depositionof the copper in cell No. 5. lf theelectrolyte in unit No.' 5 (circuit No. 5), becpnflesy too acid, vthe loosely deposited copper i 'rom cell No. 4 may be roasted, and the resulting copper oxide used to regulate copperl conte'nt ot' 5. The electrolyte the electrolyte in unit No.

a. portion ofthe in unit No. 5 is preferably 'richer and purer copper solution from the ore leachino tank or from circuit'No. 1, and both the acldity and the copper coutent of the electrolyte in unit No. is preferably at,

least partly controlled by roasted concentrated copper material, such as copper sul'- phide concentrate, metallic copper, orcoppcr 'wash waters.

'cipitate'd t e' same as sulphide'Y obtained as a precipitate inthe treatment of foul electrolyte or waste lean The reduction of the ferrie iron in unit No. 5 may be accomplished I either with sulphur dioxide, copper sulphide, or metalliccoppcrprecipitate. Copper sulphide precipitate 1s very convenient and ei'ectiveA for this purpose and is preferred; the reducing action is positive, the ampere efficiency is high, and the deposited copper is-very ure.

The e nent solution ,from electrolyticcircuit No. 2 (units No; 3 -and No. 4) containing about 0.10% copper, flowsy into the H. ,S

precipitator, where the remaining-copper is precipitated with hydrogen sulphide. TheV sulphide recipitate and thegeopperfbarren -solutionow into a separating ytank (CnS separator), where the CnS `is separa-ted from the solution. The'lCuS is transferredvtounit No. 5, to be used direct in the reduction'ff the ferrie ironproduoed by the-electrolytie deposition of Athe coppnfor, if it .is desired to roast it and,l convert it intothefo'rm of oxide, it may be conducted tothe ',roasting furnace, and, roastedl either alone for' mixed with copper sulphide ,concentrate,4 and the roasted material used to reducey the. acidit and to increase lthe coppercontent of `that -f electrolyte. The copper barren solution tllen flows to Waste, or if the solution contains other valuable metals, such as zinc, nickel, or

such as-iron and aluminum, are

precipitated;

cobalt, the excess acid is neutralized," and the neutralized and .purified solution is Athen treated to recover the other. metals,.such as zinc, nickel, and cobalt, by-any of the vwell .known methods, evaporation, crystallization, .or by tation with a reeipitant such as me or sodium hydroxide. -The precipitate is thenv separated from the barren solution and the solution wasted.

In leaching' copper ore tion, considerable wash with anacid soluwater 1s produced such as by electrolysis,

precipi-- iloj which istoo lean to' ad-d to the electrolyte.

and yet contains sufficient copper to make its recovery desirable. This lean wash yWater is conducted from the leaching tank tothe H',S preci i'tator, where the lcopper is preelectrolyte.

It is desirableto maintain Itheelectrolyte in unit No. 5 at a'roughstandard, at least inv respect to acidity and. copper. content: This may be done, Verting a portion of the solution'from unit No. 5 back to l.the leaching tank or unit No. l.,

the leaching tank or unit that ot thewaste'foul in pilrt atl least, by difrom unit No. 1 `to unit No. 5, and of old solution from unit No. 5 back to unit No.1.

Unit No. 5 is used largely to refine the impure copperI precipitatedl either electrolytically 'or chemically from the waste electrolyte orl lean -wash waters,pwhi1e at the same time some of the 'copper is deposited from 'the electrolyte itself.v All of the copper producedby'this process is producedl as the elec- `trolyt-ic metal. V l

The copper of the precipitate, used. either v as CnS or Gu goesv into solution in unit No. 5 by acting on the `ferrie iron formed b v the electrolysis in a solution containing.;4- salts of iron. If the precipitate is roasted.`

the resulting copper `oxide acts both on the acid and ferrie iron.'

lt is preferred ,to precipitate copper from the lean vashwaters and waste foul solutions after electrolysis, with hydrogen sul` phide. although other preciptants, such as metallic iron, may be used. When hydrogen .su'ilphide is used as the precipitant no more impurities ,are added to the solution while if iron is used as the pi'ecipitant an equivalent of iron goes into solution, and if other metals are to be recovered from the copper barren solution, it would be necessary Vto first eliminate this additional ir'on. i

The number of reducers and e'lectrolyzers` composing the series of reducers and electrolyzers in the precipitation of the copper from the foul solutions (circuit No. 2) may hel two or more: Usually'two will lizive the best results, and. will be so disposed that the copper which can he deposited in solid and adherent form, will be deposited in unit. No.

1` whilethe copper deposited in loose form,

-will be deposited in unit No. 2.

The regulation of the flow of the liquid through the various units and from `one unit to the next'is important. v`It is evident that if the flow is increased by a small exeessive amount of liquid, the lcumulative efl'ect. of this small amount of excess will he to flood rthe system, and if the flow is reduced to a small amount lbelow the normal,

- the rate of flow will he too slow fon etlective work, It is desirable to maintain a practically uniform condition for reduction and electrolysis evenwith a higlily'varial'ilerflow of liquid. This is preferably accomplished' as follows :-The copper solution from the `leaching tank is fed in a regulated stream into the feed tank No. l, and, theoretically at least, the same amount ofl solution flows in a regulated streamy fromv the 'feed tank into reducer No. 1, then into settler No. 1,y

and theninto cell No. 1, and 'back to the feed tank. Whilethis circulation is-goingvIon, the regi'ilatedstream of solution isfall,

the time flowing' from the leaching tank into the f eed tank No. l.; This increment of solution--tlie a'dvaii-ce-kflow-phasto be passedtothe next unit,or unit Nm 2, where again tank.

the. same constant stream of solution is'ciry culated through the-unit, while the increment, of solution-the advance flow-has to be passed from unit No.2, to the next step ot' the process.v The flow of the solution through the various units is preferably controlled througlrthe feed tanks, so that the irregularities inthe flow are taken care ofu'hile still maintaining a substantially constunt regulable or .predetermined flow through the individual units. Feed tank No. l has a regulable inflow and a regulable v underflow at `th'e bottom to the reducer: lt also has an unrestricted overflow to unit No. 2. No matter therefore how the solutionloivinef Vinto the feed tank varies, the underflow iiitoft-he reducer willbe constant, as determined by the set ot' the valve iii the underflow, andthe underflow .will remain constant until the set of the valve is changed. Similarly', feed tank No. 2 has a regulable predetermined underflow'into rediiceiNo. 2..

even with a ,variable inflow into the yfeed stricted overflow, so that. excess solution passes on and is tinally returned to the leach'- Feed tank i'o. 2, also has an unre-A ing tank. In this way the solution ,can be automatically controlled for any number o f elctrolytic units. 'The bypassing of the excess solution by the arrangement of the feed tanks permits ofwide yvariations in the ragte of flow of the solution without vdetrimental results. VT he feed tanks may be eon- Sitlered as the equivalent of any arrange intent anywhere in the circuit which will permit 'of a regulable or predetermined iin. i

deirtlow from a ool of the solution-to the roglucerin the circuit with an unrestricted overflow to the next circuit: howet'ema 'feed tank of reasonable size will be the most sii't istat-.tory arrangement.

The increment volume of solution, pie sumably as delivered from thefleachling tank, is passed throiligl'i the series of `electrolytic uiilits. and may he designated y'as thfi advance flow, and this increment ot' solu--` tion will usually vary, hut the variations are not felt in the stream ot' soluton flowing` in closed circuit in therespec ive units;- Manii'estly also, the stream of solution he. ingycircuhited in closedcircuit in one electro;

lytic `unit` may be. und usually is, different in amount from that of another unit. For example; the stream flowing 'in closed circuit 4in unit No. 2 might be twice that flowrie streamy of solution which flows from the feed tank willhe returned to the feed tank, wliil': the increment of solution passes on, 'no mat .ter what 4the rate of flow is'in the various units nor how Avariable the yincrement flow.

CnS, especially the (liiS-jieitsi1nitate'obtained from precipitating' vthe copper from the leanand foul solutions with HES., is :i iiioi'e effective reducingT agent for the ferrie iron'formed by the electrolysis in the deposition of the copper, than SO2. When a very complete or thorough reduction is desired in units No. l and No. 2, it may beL advisable to convey some of the CnS pre- -cipitate to the settlers No. 1 and No. 2,

Where theCuS Will react with the ferrie iron to reduce it. The clear overflowing so lution goes to the electrolyzers. The residual sludge, from the CuS reduction, is drawn from the bottom of the settlers, and after removing `the moisture, the residual sludge is roasted. In roasting, the sulphur is driven ofi' and'the copperconverted into the oxide, While practically all of the impurities of the CuSvresidual sludge from the Settling tanks is made insoluble, and areeliminated in the roasted ore leachm tank, While the copper goes into Ysolution an helps to enrich the electrolyte in unit No. 5 iu copper. The CuS residual sludge from the CUS reducerlof unit No. 5, may be similarly treated.

lt may be desirable to reduce the currentV density in the electrolytic deposition of the copper in units No. 3 and No. 4, especially No. 4', lWhere the copper content vof vthe electrolyte is'small. If the acidity of the sola? tion, Asay in unit No. 4, is kept very low, ^orl 'the'solution is maintained almost neutral,

there will be no great diculty in keeping down the ferrie iron, and under these condi-l tionsa iow current density can be used withV a high ampere eiciency.

ln the 'recovery ot the metals, kother than coppenfrom the diverted foul solutions, it is preferred to first precipitate the copper remaining after electrolysis, or say about .10%, with hydrogen sulphide. This will remove all of the copper, but a certain amount of acid will be generated in the deposition of the copper. It is preferred to neutralize excess acidity with lime. The

resulting calcium sulphate can be settled out of the solution. The impurities of the, iron group can be precipitated out with either lime or caustic soda. The resulti g solution will contain zinc, nickel, cobalt, ete.,

yand these metals can then be recoveredfrom the purified .solution either by elecrolysis, y

precipitation, or crystallization; kTh barren solution may be returned to the ore,'or if it is undesirable to return it to thei ore, it may be Wasted. Y

On account of the relatively high ferrous iron content oir' the electrolyte in units No. 3

and No. 4, and the low current density it is` preferred to use in the deposition of tl1e.cop. per from this lean and. foul solution, carbon :modes can be used to advantage, thus cheapening the cost of depositin the copper. Carbon. anodes will stand up. airly Well un: der good depola-riziug conditions, such lasthose in units No. 3 and No. 4and, as by 'the use of carbon. anodes 4the voltage vot' the nature of the copper solution, the sizel of the plant, and the results desired. Usually two or threeeleetrolytic units in circuit No. 1 will be most satisfactory.

1. A metallurgical process comprising' leaching-ores ot copper with an acid selution, electrolyzine; the'resulting metal solution in a series of electrolytic units each com prisin'ga feed 'taule a reducer and an elecstent How of electrolyte in a closed circuit in each of' the respective units, and bypassing excess velectroiyte threugh the feed tanks of the respective eleetroly'tic units.

ZA process comprising leachinga `ores of meta-ls with a solvent for the metals, electrolyzing the resulting solution in a series of ,electrolyt-ic units each comprising a feed, orlsolution regulating tank and an electr lyzer, maintaiuingI `pred'etermined un* deiow of solution from. the regulatingitank to ,he electrolyzer oeachunt'o the series of felectrolytic units, and maintaining an unrestricted overiow from the regulating trolyzer, maintaining; a substantially con- 1 tank of one ofthe'eleetrelyt-ie units` to the 'repjiilating tank of another eiectrclytic unit.

3, A process comprising leaehingores -ot metals yWitli a soivent Jiter' vthe metals, electrolyzing' the resulting metal solution in a series of eleetrolytio units, maintaining; a pool of solution in the circuitv of rech electrolytic unit and maintaining e predeter-- mined ioW of diiterent amounts et solution and of different metal sentent in each ein cuit of the respective clect-rolytic units y.from the pool to the `circuit of therespetive electrolytic units coxruoesingl the series und maintaining an unrestricted iiow of seliition from the pool of one eletrolyt-ic unit ttlie vpecl of ano-ther eleetrolytic unit. y v

. e. A process pcomprisiup;` eiecti'olyzing metal solutions iii a series di electrolytip units each comprising an eiectrelyizer and an electrolyte regulating tank, maintaining a ,predetermined underflow l ci? .electrolyte Yfrom the regulating tank `to the electrolyfzer of veach unit of the series o'units tile/eisetrolyteof eachunit having a diiierent /inetal' content, and 'maintaining an: unrestricted overflow of. electrolyte from the' regulating tank of'oue unitto the regulating tank eff another unit Workingl in connection with the underiovvof the respective regulating 5. A 'process oelectrolyzing copper Sciuima tions obtained from leaching copper ores and containing salts of iron comprising, clectrolyzing the solution to deposit the copper with the simultaneous regeneration of acid and ferrie iron, .reducing a portion of the ferrie irontormed by the electrolysiswith sulphur dioxide and' then anothcrportion-With copper sulphide, and repeating the cycle of deposition and reduction with sulphur dioxide and copper sulphide until the solution is sufficiently depleted of copper and regenerated in acid, and then returning the regenerated acid solution to the ore.

6. A. process of electrolyzing copper solutions containing salts of iron comprising, circulating the solution through a series of electrolytic units each comprisinga reducer and an electrolyzcr, reducing a portion of thc ferrie iron formed by the electrolysis' in the respective units with sulphur)L dioxide and another portion with copper sulphide,

and advancing thev solution *Y throdgli the electrolytic units composing tll'e series.

7. A process comprising leaching copper ore with an acid solution to entract the copper, alternately subjecting the resulting copper solution containing salts of iron to the action of a reducing agent and to the action of electrolysis todeposit' the copper and regenerate acid and repeating the cycle of leaching, reduction, and electrolysis until the solution becomes fouled with impurities, then diverting a portion of the foul solution to a separate electrolytic circuit, reducing 1 the acidity of the diverted foul solution, and

then again alternately subjecting the diverted foul solution to the action of a reducing agent and to the actionv of electrolysis, the electrolysis ot the diverted foul solution being made with a lower current densit than the elettro-lysis oi' the regular leach so ution.

S. A processV comprising leaching copper ore with an acid solution to extract the copper, alternately subjecting the resulting copper solution containing salts of ironY tothe action of sulphur dioxide and to the action of electrolysis to deposit the copper and regenerate acidY and repeating the cycle of leaching, reduc-tion, and electrolysis, until the .solution becomes fouled with impurities,

` then diverting a portion of the yfoul soluthe copper land regenerate acid and repeat-` ing the cycle of leaching, reduction, and eleci trolysis until the solutionbeconies fouled with impurities, then divertinga portion of(V the foul solution to a separate elecirolytic circuit, reducing the acidity of the solution, applying a reducing agent to the resulting solution, and electrolyzing the solution with a current density lower than that used in the regular leach solution circuit. y

' 10. A process comprising leaching copper ore With-an acid solution to extract the copper,` alternately subjecting the-resulting copl per solution to the action of a reducing agent and to'sthe action of electrolysis toydeposit Athe copper andregenerate acid and repeating the cycle of leaching, reductionfand elec# trolysis until 4the solution becomes fouled with impurities, then diverting a portion of thefoul solution to a separate electrolytic circuit', reducing the acidity of the solution, applying a reducing agent to the solution, and electrolyzing the reduced foul solution with carbon anodes.

11. A process comprising leaching copper ore with an acid solution to extract the copper, electrolyzing the resulting copper solution in a primary leaching and electrolytic circuit to deposit .the copper and regenerate acid, returning the regenerated acid solution to the ore and repeating the cycle until the solution becomes fouled with impurities, precipitating copper from -Waste foul electrolyte or from' lean wash Water, applying the copper precipitate .to arefining electrolytic circuit; and maintaining the electrolyte of the refining circuit at the desired standard by diverting a portion of the electrolye from the refining circuit to the primary leaching and electrolytic c'ircuit and adding an equivalent of fresh leach solution to the refining circuit. 1 12. A process comprising leaching copper ore containingl other metals with i. an acid solution to extract the copperl and other metals, electrolyzing the result-ing metal solution to deposit copper and regenerate.

acid, returning the regenerated acid Solution to the ore andrepeating the cycle until the solution becomes charged with, other metals' and fouled with impurities, then di.- verting a portionof the foul solution from the leaching and electrolytic circuit and precipitating the copper from said foul solution containing other metals, then precipitating undesirable impurities from the foul solution while retaining the desired metals in solution, then electrolyzing'th'e puried solution to deposit the desired metal, and

then returning the electrolyzed solution still 4containing a .small metal content the4 l'primary leaching and electrolytic circuit.

13. A process comprising leachingl copper ore with ank acid solution to extract the copv per, electrolyzing the resulting rich copper solution to depositthe copper and regenerate acid, returning the regenerated ucid solution to the ore and repeating the cycle until the solution becomes fouled with impurities, then diverting aportion of the 'foul solution from the electrolytc circuit und precipitating the copper therefrom, Washing the ore and precipitating the copper from the Wash-- I tf) Walter, then using the precipitated copper from the lean and foul solutions in the form of :modes in the rich c opper solniion to 1'; convert the impure copper of the Inceipitnte into the electrolytic metal.

VILLIAM E. GREENWJF. 

